Listing in the ivmSIP/24 blacklists indicates that your IP Address has been identified as a spam-sending server, or is in a range of IP Addresses of a host-provider that includes spending-sending servers; hence the "/24" block reference. Whether or not you operate an email-server on this IP Address, it has either sent spam or has been previously identified as such.
Ivmsip24 Reports Subnets
Subnet-based Blacklists are used to reject email from entire ranges of IP Addresses, i.e. providers that are hosting companies sending spam, as well as single IP Addresses that may fall in that range of IP Address.